Four Swiss private banks have been named in a lawsuit surrounding a wealthy Kuwaiti who was convicted of laundering money from a major pension fund.

The case surrounds the now London-based Fahad Al Rajaan, who is accused of stealing more than £670 million from Kuwait’s main pension fund, which he headed for over 30 years.

According to Middle Eastern newspaper The National, Mr Al Rajaan fled to London in 2014. Two years later he was found guilty in absentia of stealing the money a...